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Lowviz, I don't have an AL80. Sorry that I wasn't clear on the previous question. What I meant was if I should keep this tank or let it go and get a good used AL80. An AL80 is fairly cheap around here... I know people were talking about the differences between these 2 tanks multiple times, buoyancy and weight vs air capacity, but I have no experience so I can't tell how much important those are to weight in.

I’ve been given several of those tanks in the past. One thing I can say is I’ve never had to deal with one that had an internal liner, thank god!
I was given one once that was painted and had an extraordinary amount of external rust pitting down around the boot area. I sand blasted it to clean steel then sprayed on an epoxy DTM primer followed by a polyurethane topcoat. The inside was actually quite pristine. I took it to hydro and it passed!
It was a 1/2” pipe thread tank dated 1959. I dived it a few times then sold it for $50. Not the smartest business decision on my part if looking at it that way, but I did save a tank, gave the hydro shop and paint supplier some business, and made another diver happy.

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May I ask what reason made you sold it after spending money, time, and effort restoring it?

Thanks Jale,
Regarding those small flash rust spots someone mentioned above, would you think it will get bad enough to be a concern... such as exploding, bursting off, etc?

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Hi,
If it passes hydro, it would be fine. I have a few of these (metric 10L in fact) and they don't look "nice" but it is the inside that matters.
You are not going to get much by selling it. So remove the valve, have a look inside and see how it is. Even if it has rust, it is removable. A steel tanks from this period would last longer than a new alu tank.
I heard that hydro in your part of the world is quite cheap, so sent it to test; it is a cheap bet

I know people were talking about the differences between these 2 tanks multiple times, buoyancy and weight vs air capacity, but I have no experience so I can't tell how much important those are to weight in.

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Yes, these factors come into play when one considers ownership. Otherwise, when renting, one just dives what one gets.

Triple yeah. Especially as you already own it. But why not dive it, rent an Al 80 and judge for yourself?

Here is my take on the 72 vs the Al80 (I'm going off memory, so I welcome any corrections.)
The 80 only holds about 6 cu feet more than a 72 ( 77 vs 71)
The 80 weighs more than a 72-about 31 lbs vs 29 lbs
The 80 is positively buoyant at the end of a dive-about 4 lbs compared to a neutral 72. Therefore, you are swimming with 6 more pounds of mass (not to mention carrying it to and from the car and the boat or shore) for a measly 6 cu ft of gas. So some of the extra gas will be used up just from having to swim with more mass. Speaking of swimming, for me the 72 just "swims" better-but I'm only 5'8" and on the well-fed side.

Thank you to all who make this wonderful resource available, and to all the thoughtful contributors.

Triple yeah. Especially as you already own it. But why not dive it, rent an Al 80 and judge for yourself?

Here is my take on the 72 vs the Al80 (I'm going off memory, so I welcome any corrections.)
The 80 only holds about 6 cu feet more than a 72 ( 77 vs 71)
The 80 weighs more than a 72-about 31 lbs vs 29 lbs
The 80 is positively buoyant at the end of a dive-about 4 lbs compared to a neutral 72. Therefore, you are swimming with 6 more pounds of mass (not to mention carrying it to and from the car and the boat or shore) for a measly 6 cu ft of gas. So some of the extra gas will be used up just from having to swim with more mass. Speaking of swimming, for me the 72 just "swims" better-but I'm only 5'8" and on the well-fed side.

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Couv...

When the triples in the photo came into our shop in pieces...I took the time to completely restore everything and take the completed set home...

As far as this cylinder is concerned...if it came to me with a partner/bands/manifold...I would likely do the same...when a cylinder like this came into the shop with valve/plastic BP/harness...it had usually been sitting in an unheated boathouse for thirty years...it was drained/disassembled/scrapped...

In the seven years I was in the shop post retirement...we never once had anyone come into the shop to have one of these filled...I suppose there is a market...I don't know why...if this came into the shop...at the same time a prospective buyer showed up...I'd have let the cylinder/valve/BP/harness go for $10...and then likely find a reason to scrap it if the buyer wanted it serviced...

We charged $50. for re-hydro/$30. for annual VIP/$50 for annual VIP with 02 clean...any combination is worth more than this cylinder is worth...especially when you consider new low cost cylinder/valve prices from shops like DGX...

I'm pointing this one in the direction of the scrap pile...vintage....doesn't necessarily mean $...or...$$$$...